Multiple muon events observed underground

Observations are reported on events involving multiple penetrating particles recorded in a scintillator-neon flash tube telescope, at a depth of 1500 hg/cm² in the Kolar Gold Mines. From these, it is shown that: (1) the cross-section for nuclear interaction of muons of average energy ～200 GeV is ～ 6 × 10^?30 cm²/nucleon; (2) the decoherence curve for events involving two parallel muons is uniform over the range of distances from 0 to 2 metres; and (3) the angular distribution of double-parallel muons closely resembles that of single muons, implying that these two types of events are probably produced in the atmosphere in a similar manner.